1. Field of the Invention
The present invention relates to a moisture data-acquiring device (a water content information-acquiring apparatus), and an image-forming apparatus.
2. Description of Related Art
Moisture-measuring devices are known as apparatuses for acquiring information on moisture such as a water content in a sheet material like recording paper sheets and postcards.
An example of the moisture-measuring device is an optical apparatus which determines the moisture content in a sheet material by measuring light absorption or light reflection.
The optical type device isolates light of the absorption wavelength 1.94 μm of water, and light of plural reference wavelengths from continuous spectrum light, for example, by a spectroscope or a wave filter, and measures the water content by comparison of absorbance or reflectivity of the light by water with those of the reference light (e.g., Japanese Patent Application Laid-Open Nos. H05-164690, and H05-118984).
Otherwise, a technique using a monochromatic light is disclosed to avoid use of a spectroscope or a wave filter not to enlarge the apparatus (e.g., Japanese Patent Application Laid-Open No. 2000-156834).